Th2 cytokine responses are required for immunity to helminth parasites and are also responsible for the detrimental inflammation associated with allergies and asthma. Given the global prevalence of soil transmitted helminth infections, currently estimated at two billion individuals worldwide, coupled with the pandemic of allergic diseases in industrialized countries, it is critical to gain a better understanding of the pathways that control Th2 cytokine-mediated immunity and inflammation. Despite significant developments in our understanding of the pathways that control the differentiation and regulation of Th2 immunity, the innate immune cells that recognize helminth- or allergen-derived antigens and present them to naive CD4+ T cells remain poorly defined. The aims of this proposal are directed at better understand those cells and mechanisms.